There are numerous well-known drawing tools available for drawing circles, drawing and measuring lines, constructing and measuring angles, and producing geometric constructions and patterns. Generally, these devices do not provide clearly visible, direct views of vertex points through an open pivot point for drawing circles, constructing and measuring angles, and producing geometric constructions and patterns. Rather, the user must approximate the positioning of the device over the vertex point, impairing the accuracy of the positioning of circles drawn with the device, or the accuracy of the construction and measurement of angles.
One device for drawing circles that provides a clear view of vertex points through a pivot point is disclosed in U.S. Pat. No. 6,606,792, issued Aug. 13, 2003 to Stoneberg for “Drawing Tool.” The disclosed drawing tool includes a protractor portion at one end and an elongated radius arm portion extending therefrom, with a pivot disc rotatably mounted in the tool proximate the protractor portion. The radius arm rotates about the pivot disc that includes an open circular pivot point for sighting a vertex point. Although this drawing tool has enjoyed substantial commercial success, use of the tool has been somewhat limited to drawing and measuring on horizontal surfaces such as desks, overhead projectors and the like because a user must continuously press down on the pivot disc when drawing a circle to keep the tool aligned with the vertex point.
Due to the ubiquity of drawing surfaces such as, for example, vertically-oriented dry-erase or “white” boards, vertically-oriented chalk or “black” boards and horizontal surfaces such as overhead projectors and the like, in educational/classroom and workplace settings, an improved drawing tool that facilitates drawing circles in a one-handed manner would be an important improvement in the art.